1 /** 2 * \file drm_lock.c 3 * IOCTLs for locking 4 * 5 * \author Rickard E. (Rik) Faith <faith@valinux.com> 6 * \author Gareth Hughes <gareth@valinux.com> 7 */ 8 9 /* 10 * Created: Tue Feb 2 08:37:54 1999 by faith@valinux.com 11 * 12 * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas. 13 * Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California. 14 * All Rights Reserved. 15 * 16 * Permission is hereby granted, free of charge, to any person obtaining a 17 * copy of this software and associated documentation files (the "Software"), 18 * to deal in the Software without restriction, including without limitation 19 * the rights to use, copy, modify, merge, publish, distribute, sublicense, 20 * and/or sell copies of the Software, and to permit persons to whom the 21 * Software is furnished to do so, subject to the following conditions: 22 * 23 * The above copyright notice and this permission notice (including the next 24 * paragraph) shall be included in all copies or substantial portions of the 25 * Software. 26 * 27 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 28 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 29 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 30 * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR 31 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 32 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR 33 * OTHER DEALINGS IN THE SOFTWARE. 34 */ 35 36 #include "drmP.h" 37 38 static int drm_notifier(void *priv); 39 40 /** 41 * Lock ioctl. 42 * 43 * \param inode device inode. 44 * \param file_priv DRM file private. 45 * \param cmd command. 46 * \param arg user argument, pointing to a drm_lock structure. 47 * \return zero on success or negative number on failure. 48 * 49 * Add the current task to the lock wait queue, and attempt to take to lock. 50 */ 51 int drm_lock(struct drm_device *dev, void *data, struct drm_file *file_priv) 52 { 53 DECLARE_WAITQUEUE(entry, current); 54 struct drm_lock *lock = data; 55 int ret = 0; 56 57 ++file_priv->lock_count; 58 59 if (lock->context == DRM_KERNEL_CONTEXT) { 60 DRM_ERROR("Process %d using kernel context %d\n", 61 task_pid_nr(current), lock->context); 62 return -EINVAL; 63 } 64 65 DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n", 66 lock->context, task_pid_nr(current), 67 dev->lock.hw_lock->lock, lock->flags); 68 69 if (drm_core_check_feature(dev, DRIVER_DMA_QUEUE)) 70 if (lock->context < 0) 71 return -EINVAL; 72 73 add_wait_queue(&dev->lock.lock_queue, &entry); 74 spin_lock_bh(&dev->lock.spinlock); 75 dev->lock.user_waiters++; 76 spin_unlock_bh(&dev->lock.spinlock); 77 for (;;) { 78 __set_current_state(TASK_INTERRUPTIBLE); 79 if (!dev->lock.hw_lock) { 80 /* Device has been unregistered */ 81 ret = -EINTR; 82 break; 83 } 84 if (drm_lock_take(&dev->lock, lock->context)) { 85 dev->lock.file_priv = file_priv; 86 dev->lock.lock_time = jiffies; 87 atomic_inc(&dev->counts[_DRM_STAT_LOCKS]); 88 break; /* Got lock */ 89 } 90 91 /* Contention */ 92 schedule(); 93 if (signal_pending(current)) { 94 ret = -ERESTARTSYS; 95 break; 96 } 97 } 98 spin_lock_bh(&dev->lock.spinlock); 99 dev->lock.user_waiters--; 100 spin_unlock_bh(&dev->lock.spinlock); 101 __set_current_state(TASK_RUNNING); 102 remove_wait_queue(&dev->lock.lock_queue, &entry); 103 104 DRM_DEBUG("%d %s\n", lock->context, 105 ret ? "interrupted" : "has lock"); 106 if (ret) return ret; 107 108 /* don't set the block all signals on the master process for now 109 * really probably not the correct answer but lets us debug xkb 110 * xserver for now */ 111 if (!file_priv->master) { 112 sigemptyset(&dev->sigmask); 113 sigaddset(&dev->sigmask, SIGSTOP); 114 sigaddset(&dev->sigmask, SIGTSTP); 115 sigaddset(&dev->sigmask, SIGTTIN); 116 sigaddset(&dev->sigmask, SIGTTOU); 117 dev->sigdata.context = lock->context; 118 dev->sigdata.lock = dev->lock.hw_lock; 119 block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask); 120 } 121 122 if (dev->driver->dma_ready && (lock->flags & _DRM_LOCK_READY)) 123 dev->driver->dma_ready(dev); 124 125 if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT)) 126 { 127 if (dev->driver->dma_quiescent(dev)) { 128 DRM_DEBUG("%d waiting for DMA quiescent\n", 129 lock->context); 130 return -EBUSY; 131 } 132 } 133 134 if (dev->driver->kernel_context_switch && 135 dev->last_context != lock->context) { 136 dev->driver->kernel_context_switch(dev, dev->last_context, 137 lock->context); 138 } 139 140 return 0; 141 } 142 143 /** 144 * Unlock ioctl. 145 * 146 * \param inode device inode. 147 * \param file_priv DRM file private. 148 * \param cmd command. 149 * \param arg user argument, pointing to a drm_lock structure. 150 * \return zero on success or negative number on failure. 151 * 152 * Transfer and free the lock. 153 */ 154 int drm_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv) 155 { 156 struct drm_lock *lock = data; 157 unsigned long irqflags; 158 void (*tasklet_func)(struct drm_device *); 159 160 if (lock->context == DRM_KERNEL_CONTEXT) { 161 DRM_ERROR("Process %d using kernel context %d\n", 162 task_pid_nr(current), lock->context); 163 return -EINVAL; 164 } 165 166 spin_lock_irqsave(&dev->tasklet_lock, irqflags); 167 tasklet_func = dev->locked_tasklet_func; 168 dev->locked_tasklet_func = NULL; 169 spin_unlock_irqrestore(&dev->tasklet_lock, irqflags); 170 if (tasklet_func != NULL) 171 tasklet_func(dev); 172 173 atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]); 174 175 /* kernel_context_switch isn't used by any of the x86 drm 176 * modules but is required by the Sparc driver. 177 */ 178 if (dev->driver->kernel_context_switch_unlock) 179 dev->driver->kernel_context_switch_unlock(dev); 180 else { 181 if (drm_lock_free(&dev->lock,lock->context)) { 182 /* FIXME: Should really bail out here. */ 183 } 184 } 185 186 unblock_all_signals(); 187 return 0; 188 } 189 190 /** 191 * Take the heavyweight lock. 192 * 193 * \param lock lock pointer. 194 * \param context locking context. 195 * \return one if the lock is held, or zero otherwise. 196 * 197 * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction. 198 */ 199 int drm_lock_take(struct drm_lock_data *lock_data, 200 unsigned int context) 201 { 202 unsigned int old, new, prev; 203 volatile unsigned int *lock = &lock_data->hw_lock->lock; 204 205 spin_lock_bh(&lock_data->spinlock); 206 do { 207 old = *lock; 208 if (old & _DRM_LOCK_HELD) 209 new = old | _DRM_LOCK_CONT; 210 else { 211 new = context | _DRM_LOCK_HELD | 212 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ? 213 _DRM_LOCK_CONT : 0); 214 } 215 prev = cmpxchg(lock, old, new); 216 } while (prev != old); 217 spin_unlock_bh(&lock_data->spinlock); 218 219 if (_DRM_LOCKING_CONTEXT(old) == context) { 220 if (old & _DRM_LOCK_HELD) { 221 if (context != DRM_KERNEL_CONTEXT) { 222 DRM_ERROR("%d holds heavyweight lock\n", 223 context); 224 } 225 return 0; 226 } 227 } 228 229 if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) { 230 /* Have lock */ 231 return 1; 232 } 233 return 0; 234 } 235 236 /** 237 * This takes a lock forcibly and hands it to context. Should ONLY be used 238 * inside *_unlock to give lock to kernel before calling *_dma_schedule. 239 * 240 * \param dev DRM device. 241 * \param lock lock pointer. 242 * \param context locking context. 243 * \return always one. 244 * 245 * Resets the lock file pointer. 246 * Marks the lock as held by the given context, via the \p cmpxchg instruction. 247 */ 248 static int drm_lock_transfer(struct drm_lock_data *lock_data, 249 unsigned int context) 250 { 251 unsigned int old, new, prev; 252 volatile unsigned int *lock = &lock_data->hw_lock->lock; 253 254 lock_data->file_priv = NULL; 255 do { 256 old = *lock; 257 new = context | _DRM_LOCK_HELD; 258 prev = cmpxchg(lock, old, new); 259 } while (prev != old); 260 return 1; 261 } 262 263 /** 264 * Free lock. 265 * 266 * \param dev DRM device. 267 * \param lock lock. 268 * \param context context. 269 * 270 * Resets the lock file pointer. 271 * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task 272 * waiting on the lock queue. 273 */ 274 int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context) 275 { 276 unsigned int old, new, prev; 277 volatile unsigned int *lock = &lock_data->hw_lock->lock; 278 279 spin_lock_bh(&lock_data->spinlock); 280 if (lock_data->kernel_waiters != 0) { 281 drm_lock_transfer(lock_data, 0); 282 lock_data->idle_has_lock = 1; 283 spin_unlock_bh(&lock_data->spinlock); 284 return 1; 285 } 286 spin_unlock_bh(&lock_data->spinlock); 287 288 do { 289 old = *lock; 290 new = _DRM_LOCKING_CONTEXT(old); 291 prev = cmpxchg(lock, old, new); 292 } while (prev != old); 293 294 if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) { 295 DRM_ERROR("%d freed heavyweight lock held by %d\n", 296 context, _DRM_LOCKING_CONTEXT(old)); 297 return 1; 298 } 299 wake_up_interruptible(&lock_data->lock_queue); 300 return 0; 301 } 302 303 /** 304 * If we get here, it means that the process has called DRM_IOCTL_LOCK 305 * without calling DRM_IOCTL_UNLOCK. 306 * 307 * If the lock is not held, then let the signal proceed as usual. If the lock 308 * is held, then set the contended flag and keep the signal blocked. 309 * 310 * \param priv pointer to a drm_sigdata structure. 311 * \return one if the signal should be delivered normally, or zero if the 312 * signal should be blocked. 313 */ 314 static int drm_notifier(void *priv) 315 { 316 struct drm_sigdata *s = (struct drm_sigdata *) priv; 317 unsigned int old, new, prev; 318 319 /* Allow signal delivery if lock isn't held */ 320 if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock) 321 || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context) 322 return 1; 323 324 /* Otherwise, set flag to force call to 325 drmUnlock */ 326 do { 327 old = s->lock->lock; 328 new = old | _DRM_LOCK_CONT; 329 prev = cmpxchg(&s->lock->lock, old, new); 330 } while (prev != old); 331 return 0; 332 } 333 334 /** 335 * This function returns immediately and takes the hw lock 336 * with the kernel context if it is free, otherwise it gets the highest priority when and if 337 * it is eventually released. 338 * 339 * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held 340 * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause 341 * a deadlock, which is why the "idlelock" was invented). 342 * 343 * This should be sufficient to wait for GPU idle without 344 * having to worry about starvation. 345 */ 346 347 void drm_idlelock_take(struct drm_lock_data *lock_data) 348 { 349 int ret = 0; 350 351 spin_lock_bh(&lock_data->spinlock); 352 lock_data->kernel_waiters++; 353 if (!lock_data->idle_has_lock) { 354 355 spin_unlock_bh(&lock_data->spinlock); 356 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT); 357 spin_lock_bh(&lock_data->spinlock); 358 359 if (ret == 1) 360 lock_data->idle_has_lock = 1; 361 } 362 spin_unlock_bh(&lock_data->spinlock); 363 } 364 EXPORT_SYMBOL(drm_idlelock_take); 365 366 void drm_idlelock_release(struct drm_lock_data *lock_data) 367 { 368 unsigned int old, prev; 369 volatile unsigned int *lock = &lock_data->hw_lock->lock; 370 371 spin_lock_bh(&lock_data->spinlock); 372 if (--lock_data->kernel_waiters == 0) { 373 if (lock_data->idle_has_lock) { 374 do { 375 old = *lock; 376 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT); 377 } while (prev != old); 378 wake_up_interruptible(&lock_data->lock_queue); 379 lock_data->idle_has_lock = 0; 380 } 381 } 382 spin_unlock_bh(&lock_data->spinlock); 383 } 384 EXPORT_SYMBOL(drm_idlelock_release); 385 386 387 int drm_i_have_hw_lock(struct drm_device *dev, struct drm_file *file_priv) 388 { 389 return (file_priv->lock_count && dev->lock.hw_lock && 390 _DRM_LOCK_IS_HELD(dev->lock.hw_lock->lock) && 391 dev->lock.file_priv == file_priv); 392 } 393 394 EXPORT_SYMBOL(drm_i_have_hw_lock); 395